look for products marked eko. ecological products in sweden that are of made out of milk require to be only feed with ecological food, which only ecological grass does, but even the nromal butter is grass feed because pellets or any other stuff is expensive

Always go for products that have been manufactured in Sweden. They have one of best feeding program for their cattle and birds. They have minimal antibiotic usage here as well. I've just moved from the UK where I only brought local grass fed or organic meat but here you can buy the normal products and know that is would have been raised well. Grains will always be fed to a certain degree especially in winter. I cooked a roast chicken the other day which I brought from ICA and it was lovely. Meat is so much nicer here. (expensive but good).

I've never tried to buy it (the ordinary butter is pretty good already as per other responses), but if I were to, then I would try Cajsa Varg (upmarket Swedish food), or Urban Deli (less foodie but more hipster version of said). I think you could try the little shop next to/owned by Gastrologik also. Maybe also Ostbutiken on Odengatan, or one of the diary stands in Ostermalmshallen? All these places are worth a browse if you're any kind of foodie, but sadly not exactly cheap.

I've seen unpasteurised butter from Normandy and butter from the Italian alps in Cajsa Varg for sure.

even with eko/organic dairy produce, you can have additional feeds, provided that these are also organic etc.. the whole animal and food chain needs to be organic to comply.

I know some who feed grains, generally their own home grown oats, which are just crushed or rolled prior to feeding as a boost to silage or hay in winter. Of course those wishing to sell their milk or meat as organic, will need to grow their oats under organic rules.

What you will get much less of in Sweden or Norway than anywhere else in Europe are antibiotic use with Livestock. (Lowest in the EU). Also all the various growth hormones are banned in Europe. So even just buying an off the shelf Swedish produce meat or dairy product you are getting goods that are on a par with some other countries Organic / Niche stuff.

Avoid Danish, although also Scandic they don't have much land for their population or scale of animal production that they pursue, so it's much more intensive, more use of antibiotics in preventative treatments etc..